During the operation of machinery and other equipment, it is often necessary to monitor the operating parameters of the equipment. Limits exist for operating parameters to limit the absolute magnitudes of the parameters and the duration in which a parameter exists at a given magnitude. For example, in the operation of a steam turbine, it is necessary to set control limits for various operating parameters such as the steam temperature within the turbine.
Typically, the limits of an operating parameter are defined by both the magnitude and duration of a limit exceedance. A parameter may go above a set limit for a short amount of time without adverse consequences; however, if the parameter exceeds the limit for long periods of time, the equipment may be damaged. Also, a gradual rate of change for a parameter may have no adverse consequences; whereas a sudden increase or decrease in the magnitude of a parameter may lead to equipment damage. For example, the steam temperature in a turbine may increase slowly over time with no equipment damage, but a sudden increase in temperature may cause serious damage to the steam turbine.
Current methods for measuring parameter limit exceedance detect the moment in time in which a limit is exceeded. A timer is then triggered to determine the duration for which the parameter exceeds the limit. Corrective action typically is taken only after the timer has run for a predetermined period while the parameter exceeds its magnitude limit. However, change in the parameter value while in excess of the magnitude limit, and perhaps even before the limit is reached, may be equally important for the determination or prediction of equipment damage. Therefore, there exist a need in the art for a system and method for monitoring and detecting parameter changes in the parameter magnitude other than just limit exceedance.